Mingliang DING,Qiuhong PU,Chunqiong GAO,Pingrong YUAN,Zhenxi SU*

1.Institute of Food Crops,Yunnan Academy of Agricultural Sciences,Kunming 650205,China;

2.Xuanwei Middle School,Xuanwei 655400,China;3.Xuanwei Municipal Bureau of Agriculture,Xuanwei 655400,China

Principal Component Analysis on Traits Related to Lodging Resistance of Plateau Japonica Rice

Mingliang DING1,Qiuhong PU2,Chunqiong GAO3,Pingrong YUAN1,Zhenxi SU1*

1.Institute of Food Crops,Yunnan Academy of Agricultural Sciences,Kunming 650205,China;

2.Xuanwei Middle School,Xuanwei 655400,China;3.Xuanwei Municipal Bureau of Agriculture,Xuanwei 655400,China

[Objective]This study was conducted to investigate the main factors affecting the lodging resistance of plateau japonica rice.[Method]Twenty agronomic traits related to lodging resistance of plateau japonica rice were analyzed by principal component analysis and correlation analysis among 26 varieties/lines of plateau japonica rice.[Result]The lodging resistance of the 26 varieties/lines had great difference among different agronomic traits.Plant height,and wall thickness of the 4th, 3rdand 2ndinternodes under the panicle had the most important influence on lodging resistance,while the diameter of the 3rd,2nd,4th,1stnodes under the panicle,length of the 4thand 3rdinternodes under the panicle,wall thickness of the 1stinternode under the panicle had less influence.The other nine agronomic traits of rice culm did not affect or indirectly affected lodging resistance through above-mentioned agronomic traits.Lodging resistance had significant correlations with plant height,length of the 4thand 3rdinternodes under the panicle,wall thickness of the 1st,2nd,3rdand 4thinternodes under the panicle and diameter of the 1st,2nd,3rdand 4thnode sunder the panicle,had insignificant correlations with panicle length,panicle weight,length of the 1stand 2ndinternodes under the panicle,diameter of the 1st,2nd,3rdand 4thinternodes under the panicle,diameter of the 5thnode under the panicle.[Conclusion]More attention should be paid to the main factors affecting lodging resistance in breeding to improve lodging resistance of plateau japonica rice.

Plateau japonica rice;Lodging resistance;Agronomic traits;Principal component analysis

R ice is widely planted on 1 million hectares in Yunnan Province,in which plateau japonica rice occupies half of the area. Lodging,one of the most important factors affecting the production of japonica rice,not only decreases rice yield and quality,but also bring difficulties to rice harvest.Rice lodging is a complex quantitative trait,which has certain relation with the internal factors of rice such as plant height,culm trait and biological yield,but also is affected by extrinsic factors like cultivation and management measures and climate[1-4].Lodging resistance of plateau japonica rice has been rarely reported so far.Ding et al.[5]believed that rice lodging resistance had insignificant correlation with panicle length,panicle weight and internode diameter,but significant or extremely significant correlations with plant height,length of internodes under the panicle,wall thickness of internodes under the panicle and diameter of internodes under the panicle.However,the effects or contributions of these factors on lodging resistance of rice remain elusive.Therefore,plant height,panicle weight,panicle length,internode length,internode wall thickness,internode diameter and node diameter all of which were related to lodging resistance of commonly planted plateau japonica rice varieties were measured to conduct correlation analysis and principal component analysis,with an

Materials and Methods

Materials

Fifteen commonly planted rice varieties and 11 newly bred lines by Institute of Food Crops,Yunnan Academy of Agricultural Sciences were selected as the experimental materials,as shown in Table 1.

The field trials were carried out at Yiliang County(103.14°E,24.92°N at an elevation of 1 500 m)and Songming County(102.81°E,25.22°N at an elevation of 1 900 m)of Kunming City,China in 2010.According to their adaptability,Yunjing 32,Yunjing 31, Yinguang,H150,H149,H148,08-3, and 09-1 were grown at Songming and the other varieties/lines at Yiliang. Bean was planted before them in both bases.Rice seeds were sown in March 2010 under plastic films.Then, 45-day-old seedlings were transplanted into filed in May,spacing(27+15) cm×12.9 cm,with 20 rows for each rice variety/line.Fertilizers and water were supplied timely and appropriately.Soils in both bases were sampled on April 30,2010,and sent to the Institute of Agricultural Environment and Resources,Yunnan Academy of Agricultural Sciences for chemical analysis and test.The results revealed that soil sample collected from Yiliang County maintained a pH at 7.45,and contained 3.04%organic matter,86.15 mg/kg available nitrogen(N),9.37 mg/kg available phosphorus(P),and 117.30 mg/kg available potassium(K); the soil sample from Songming County had a pH at 6.94,and contained 4.55%organic matter,132.17 mg/kg available nitrogen(N),10.71 mg/kg available phosphorus(P)and 67.38 mg/kg available potassium(K).According to the soil properties,246.0 kg/hm2pure N was applied in both bases,65%as base and tillering fertilizer,and 35%as panicle fertilizer (base fertilizer∶tillering fertilizer=6∶4, first fertilization∶second fertilization at panicle stage=6∶4).Moreover,the base fertilizer also contained 127.5 kg/hm2pure P,102 kg/hm2pure K and 30 kg/hm2pure Zn.

Methods

Test on rice lodging resistance

The lodging resistance of rice was measured at maturity(95%spikelets at waxen maturity).The lodging of rice is divided into four levels.In detail,level 1 was defined as rice stems were straight or mostly straight;level 2 was defined as rice stems leaned at an angle less than 45°;level 3 was defined as rice stems leaned at an angle more than 45°;level 4 was defined as rice stems completely leaned down to the ground.In this study,rice varieties of level 1 and level 2 were considered as lodging resistant,and those of level 3 and level 4 as lodging.

Determination of agronomic traits

At maturity,nine seedlings at three sites for each variety/line were collected with roots,leaf sheathes, leaves and panicle.Then,plant height,panicle length,panicle weight, the length,wall thickness,diameter of the 1st,2nd,3rd,4thinternodes under the panicle,and the diameter of the 1st,2nd,3rd,4th,5thnodes under the panicle were measured.Among them, plant height,panicle length,internode length were measured with a ruler (accurate to 0.1 cm);panicle weight was measured with an electronic balance(accurate to 0.01g);the wall thickness of internodes and the diameter of internodes and nodes were measured with a vernier caliper (accurate to 0.002 cm).The averages of nine seedlings of each variety/line were finally calculated.

Data analysis

SPSS 17.0 software was employed for correlation analysis and principal component analysis.

Results and Analysis

Lodging resistance of these plateauJaponicarice varieties/lines

As shown in Table 1,among the 26 plateau japonica rice varieties/lines 15 exhibited better resistance to lodging.The traits related to lodging resistance showed abundant variation among these varieties/lines,among which the length of the 4thinternode under the panicle had the largest variation coefficient(29.2%),while plant height and the diameter of the 4thnode under the panicle had the smallest (7.3%).The variation coefficients of other traits were also significantly different.The 20 lodging related traits were listed according to their variation coefficients from large to small as length of the 4thinternode under the panicle＞panicle weight＞wall thickness of the 4thinternode under the panicle＞length of the 3rd internode under the panicle＞wall thickness of the 1stinternode under the panicle＞wall thickness of the 2ndinternode under the panicle＞wall thickness of the 3rdinternode under the panicle＞diameter of the 1stinternode under the panicle＞diameter of the 1stnode under the panicle＞diameter of the 5thnode under the panicle＞length of the 1stinternode under the panicle＞diameter of the 4thinternode under the panicle＞length of the 2ndinternode under the panicle＞diameter of the 3rdnode under the panicle＞diameter of the 2ndnode under the panicle＞panicle length＞diameter of the 2ndnode under the panicle＞diameter of the 3rdinternode under the panicle＞plant height=diameter of the 4thnode under the panicle.

The larger variation coefficients for length of the 4thinternode under the panicle,panicle weight,wall thickness of the 4thinternode under the panicle and length of the 3rdinternode under the panicle suggested that improving these traits through appropriate breeding and cultivation measures could greatly improve the lodging resistance of plateau japonica rice varieties.The large variation coefficients for wall thickness of the 1st,2nd,3rdinternodes under the panicle and diameter of the 1stinternode under the panicle indicated that improving these traits through appropriate breeding and cultivation measures could improve the lodging resistance of plateau japonica rice varieties to some extent. The small variation coefficients and difference for plant height and diameter of the 4thnode under the panicle among the rice varieties/lines indicated that the lodging resistance of plateau japonica rice varieties could not be improved through improving these traits.

Correlation between lodging resistance and agronomic traits of these plateaujaponicarice varieties/lines

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Correlation analysis showed thatamong the 20 traits measured,11 had significant or extremely significant correlations with lodging resistance. Among the 11 traits,plant height, length of the 3rdand 4thinternodes under the panicle was negatively correlated with lodging resistance,while wall thickness of the 1st,2nd,3rdand 4thinternodes under the panicle,diameter of the 1st,2nd,3rdand 4thnodes under the panicle was positively correlated with lodging resistance.Panicle length, panicle weight,length of the 1stand 2ndinternodes under the panicle,diameter of the 1st,2nd,3rdand 4thinternodes under the panicle,diameter of the 5thnode under the panicle showed no significant correlations with lodging resistance in these plateau japonica rice varieties/lines.In addition,there were complicated correlations among these culm traits,as shown in Table 2.In summary,plant height,length of the 3rdand 4thinternodes under the panicle, wall thickness of the 1st,2nd,3rdand 4thinternodes under the panicle,diameter of the 1st,2nd,3rdand 4thnodes under the panicle had greater influence on lodging resistance of plateau japonica rice.So,appropriately reducing plant height,length of the 3rdand 4thinternodes under the panicle,increasing wall thickness of the 1st,2nd,3rdand 4thinternodes under the panicle,diameter of the 1st,2nd,3rdand 4thnodes through breeding and cultivation measures will help to enhance the lodging resistance of plateau japonica rice.

Principal component analysis on lodging resistance and related agronomic traits of plateaujaponicarice

In order to measure the contribution of lodging resistance related factors,principal component analysis on the 20 traits of plateau japonica rice was carried out.As shown in Table 3, five principal components whose eigenvalues were greater than 1 were extracted,and their cumulative contribution rate was 88.943%,which could explain 88.943%of the variance. Therefore,the five principal components epitomized most information of lodging resistance and related culm traits of plateau japonica rice.

It could be concluded from Table 4 that among Principal component 1, the diameter of the 2ndinternode underthe panicle,the diameter of the 3rd,2nd, 4thand 1stnodes under the panicle had larger loading.The diameter of the 2ndinternode under the panicle had no significant correlation with lodging resistance,while the diameter of the 3rd, 2nd,4thand 1stnodes under the panicle had significantly positive correlations with lodging resistance,indicating increasing diameter of the nodes under the panicle especially diameter of the 3rdnode under the panicle helped to improve the lodging resistance of plateau japonica rice.Among Principal component 2,plant height,panicle length,wall thickness of the 4thinternode under the panicle and length of the 1st internode under the panicle had greater loading.Panicle length and length of the 1stinternode under the panicle showed no significant correlation with lodging resistance,while plant height exhibited extremely significant negative correction,and the wall thickness of the 4thinternode under the panicle showed extremely significant positive correlation with lodging resistance,indicating appropriately reducing plant height and increasing wall thickness of the 4thinternode under the panicle could improve the lodging resistance of plateau japonica rice. Among Principal component 3,the length of the 4thinternode under the panicle,wall thickness of the 1stinternode under the panicle,length of the 1st, 2ndand 3rdinternodes under the panicle had greater loading.The length of the 1stand 2ndinternodes under the panicle showed no significant correlation with lodging resistance,while the length of the 4thand 3rdinternodes under the panicle showed significant negative correlation,and the wall thickness of the 1stinternode under the panicle exhibited significant positive correlation with lodging resistance,indicating that appropriately reducing the 4thand 3rdinternodes under the panicle and increasing the wall thickness of the 1stinternode under the panicle helped to improve the lodging resistance of plateau japonica rice.Among Principal component 4,the wall thickness of the 1stinternode under the panicle, length of the 2ndinternode under the panicle,wall thickness of the 2ndinternode under the panicle,panicle weight and wall thickness of the 3rdinternode under the panicle had larger loading.The length of the 2ndinternode under the panicle and panicle weight had no significant correlation with lodging resistance,while the wall thickness of the 1st,2ndand 3rdinternodes under the panicle showed significant positive correlation with lodging resistance,indicating that increasing the wall thickness of the 1st,2ndand 3rdinternodes under the panicle could improve the lodging resistance of plateau japonica rice.Among Principal component 5, panicle length,diameter of the 4thand 5thnodes under the panicle,length of the 2ndinternode under the panicle and panicle weight had larger loading.Panicle length,diameter of the 5thnode under the panicle,length of the 2ndinternode under the panicle and panicle weight had no significant correlation with lodging resistance,while diameter of the 4thnode under the panicle ex-hibited significant positive correlation with lodging resistance,indicating that increasing the diameter of the 4thnode under the panicle could improve the lodging resistance of plateau japonica rice.

Table 3The characteristic value and cumulative contribution rate of five principal components

Table 4Component matrix of lodging resistance and related traits of plateau japonica rice

In summary,the lodging resistance of these plateau japonica rice varieties(lines)had the largest eigenvector on Principal component 2 (-0.632),indicating that Principal component 2 were most closely related to lodging resistance,while plant height,wall thickness of the 4th,3rdand 2ndinternodes under the panicle had larger loading among Principal component 2(0.918,-0.548,-0.503 and -0.481),and extremely significant correlations with lodging resistance (r=-0.661**,r=0.665**,r=0.619**and r=0.606**).In addition,among the traits those showed significant positive correlations with lodging resistance, the diameter of the 3rd,2nd,4thand 1stnodes under the panicle had greater loading on the Principal component 1; the length of the 4thand 3rdinternodes under the panicle and the wall thickness of the 1stinternode under the panicle had greater loading on Principal component 3;the wall thickness of the 1st,2ndand 3rdinternodes under the panicle had greater loading on Principal component 4;the diameter of the 4thnode under the panicle had greater loading on Principal component 5.All the results revealed that plant height, and wall thickness of the 4th,3rdand 2ndinternodes under the panicle had the most important influence on lodging resistance,while the diameter of the 3rd,2nd,4th,1stnodes under the panicle, length of the 4thand 3rdinternodes under the panicle,wall thickness of the 1stinternode under the panicle had less influence.The other nine agronomic traits of rice culm did not affect or indirectly affected lodging resistance through above-mentioned agronomic traits.

Conclusion and Discussion

Lodging has been one of the main factors deceasing rice production.Studies have shown that plant height[5,7-12],internode length[5,7-16],internode diameter[5,9,12,13],internode wall thickness[5,9,12-14],node diameter[5],panicle length[14]and panicle weight[11,14]are closely related to lodging resistance, and their influence are different[18].Our results showed that plant height,wall thickness of the 4th,3rdand 2ndinternodes under the panicle had the most important influence on the lodging resistance of plateau japonica rice,followed by the diameter of the 3rd,2nd,4th, 1stnodes under the panicle,length of the 4thand 3rdinternodes under the panicle,wall thickness of the 1stinternode under the panicle,while other nine agronomic traits of rice culm had no significant influence.To obtain excellent rice varieties highly resistant to lodging,it is important to improve plant height,wall thickness of the 4th,3rdand 2ndinternodes under the panicle in breeding.

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Responsible editor:Qingqing YIN

Responsible proofreader:Xiaoyan WU

高原粳稻抗倒性相關性狀的主成分分析

丁明亮1，浦秋紅2，高春瓊3，袁平榮1，蘇振喜1*
（1.云南省農(nóng)業(yè)科學院糧食作物研究所，云南昆明650205；2.云南省宣威市民族中學，云南宣威655400；3.云南省宣威市農(nóng)業(yè)局，云南宣威655400）

[目的]探討影響高原粳稻抗倒性的主要因素。[方法]該試驗以26份云南高原粳稻品種（系）為供試材料，對高原粳稻抗倒性及其相關的20個農(nóng)藝性狀進行了相關分析和主成分分析。[結果]供試材料的抗倒性在在不同性狀間存在較大差異。株高、穗下第4、3、2節(jié)間壁厚4個性狀對抗倒性影響最大，而穗下第3、2、4、1節(jié)直徑、穗下第4、3節(jié)間距離和穗下第1節(jié)間壁厚7個性狀對抗倒性影響較小，其余9個莖稈性狀不影響或者通過上述莖稈性狀而間接影響抗倒性。株高、穗下第4、3節(jié)間距離、穗下第1、2、3、4節(jié)間壁厚和穗下第1、2、3、4節(jié)直徑共11個農(nóng)藝性狀與抗倒性存在顯著相關關系，而穗長、穗重、穗下第1、2節(jié)間距離、穗下第1、2、3、4節(jié)間直徑和穗下第5節(jié)直徑9個性狀與抗倒性的相關性不顯著。[結論]在高原粳稻的育種中，應注重這些主要影響因素的改良以提高高原粳稻品種（系）抗倒性。

高原粳稻；抗倒性；農(nóng)藝性狀；主成分分析attempt to clarify their effects on lodging resistance and provide theoretical basis for breeding and cultivation of lodging-resistant of plateau japonica rice varieties(lines).

常規(guī)水稻新品種選育及產(chǎn)業(yè)化開發(fā)項目（2010BB013）；云南省技術創(chuàng)新人才培養(yǎng)項目（2010CⅠ075）。

丁明亮(1987-)，男，江西豐城人，研究實習員，從事水稻遺傳育種研究，E-mail：414108128@qq.com。*通訊作者，研究員，從事水稻遺傳育種研究，E-mail：suzhengx@yahoo. com.cn。

2015-03-05

修回日期 2015-05-28

Supported by Program for the Breeding and Industrial Development of Conventional Rice Varieties(2010BB013);Training Plan of Technological Innovation Talents of Yunnan Province(2010CI075).

*Corresponding author.E-mail:suzhengx@yahoo.com.cn

Received:March 5,2015 Accepted:May 28,2015